An aircraft can include one or more fluid lines, e.g., tubing through which an aircraft fluid, e.g., fuel or other aircraft fluid, is transported. In some situations, a fluid line can be an inner tube used to transmit fluid. The inner tube can be surrounded by an outer tube (often referred to as a “sock”) to contain fluid in the event that the inner tube leaks, and to direct the leaked fluid to a collection point or separate chamber where it can be safely discharged. In such situations, the outer tube serves as a secondary containment mechanism that directs leaked fluid away from a source of the leak. The outer tube prevents leaked fluid from leaking into the fuselage or onto aircraft components, as the fluid could pose a safety hazard or damage the components or both. In some cases, the placement of the fluid lines does not allow an outer tube to be connected to a collection point. For example, if a fluid line terminates at a bulkhead, the outer tube of the fluid line must also terminate at the bulkhead.